Magnetometer Calibration for Vehicle Positioning

Solution Overview

Problem

Existing methods for determining the position and orientation of a vehicle using a magnetometer face challenges in obtaining an accurate initial estimate of the yaw angle, as the magnetometer calibration varies over time and is difficult to calibrate in a moving vehicle with an uncontrolled environment, leading to decreased accuracy.

Innovation Solution

A method and system that includes a magnetometer calibration module to update scale and offset coefficients based on tests for accuracy, interference, and yaw angle changes, ensuring accurate initial estimates and continuous calibration for improved position and orientation determination.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If magnetometer calibration is performed using pre-recorded scale and offset coefficients, then the initial yaw angle estimate can be obtained, but the accuracy decreases over time as calibration varies

Engineering Contradiction:

Improveinitial yaw angle estimate accuracyVSAvoidcalibration stability over time

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent performs magnetometer calibration in advance during a dedicated calibration phase before the vehicle operates in its normal environment. This preliminary calibration establishes accurate scale and offset coefficients that are stored for use during operation, avoiding the need to maintain calibration in changing operational conditions.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent compensates for potential calibration drift by performing calibration beforehand in a controlled environment. The calibrated values serve as a baseline that compensates for subsequent variations during vehicle operation, cushioning against accuracy degradation over time.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

2Adaptability or versatility

If magnetometer calibration is performed in a moving vehicle with uncontrolled environment, then continuous calibration is possible, but the calibration accuracy deteriorates

Engineering Contradiction:

Improvecalibration capability during operationVSAvoidcalibration accuracy

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The patent performs magnetometer calibration in advance during a dedicated calibration phase before the vehicle operates in its normal environment. This preliminary calibration establishes accurate scale and offset coefficients that are stored for use during operation, avoiding the need to maintain calibration in changing operational conditions.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent distinguishes between different operational phases: a controlled calibration phase for accurate coefficient determination, and a normal operation phase for using these coefficients. Each phase has appropriate characteristics - the calibration phase provides controlled conditions while the operation phase provides real-world applicability.

Inventive Principle:

Principle #3Local quality

3Productivity

If the merge algorithm is initialized with a poor initial yaw angle estimate, then the algorithm can start, but convergence speed decreases

Engineering Contradiction:

Improvealgorithm convergence speedVSAvoidinitial yaw angle estimate accuracy

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

The patent performs magnetometer calibration in advance during a dedicated calibration phase before the vehicle operates in its normal environment. This preliminary calibration establishes accurate scale and offset coefficients that are stored for use during operation, avoiding the need to maintain calibration in changing operational conditions.

Inventive Principle:

Principle #10Preliminary action

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach enhances the accuracy of the initial yaw angle estimate and speeds up the convergence of the position and orientation estimation algorithm, improving the reliability and efficiency of vehicle navigation systems.

Implementation Method 1

a magnetometer including at least two measurement axes; measuring, by means of the magnetometer, a first raw-measurement vector containing a raw component for each of the measurement axes, each component encoding the amplitude and the direction of the orthogonal projection of the magnetic field which passes through this magnetometer

Methodology Applied

Scientific EffectMagnetic field measurement: Magnetic Field

Data Source

PatentUS11519730B2Method for determining the position and orientation of a vehicle

Publication Date: 2022.12.06 COMMISSARIAT A LENERGIE ATOMIQUE ET AUX ENERGIES ALTERNATIVES

AI summary

A method for determining the position and orientation of a vehicle, this method including measuring, with a magnetometer, a raw-measurement vector; obtaining a reference vector encoding, in a terrestrial reference frame, the amplitude and the direction of the geomagnetic field, the components of the reference vector being obtained from a pre-recorded model of the geomagnetic field and not measured by the magnetometer; then only if the margin of error in an estimate of the orientation of the vehicle is below a predetermined threshold, updating the pre-recorded data from which scale and offset coefficients used for correcting the raw measurement from the magnetometer are obtained, this update being performed using the raw vector, the reference vector and the new estimate of the orientation of the vehicle.